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I recently bought a used C50 off ebay but have a problem. I've only had 3 bikes before but on all of them the rear brake pushed into the bridge then you screwed in a nut from the other side. The hole in the bridge on the C50 seems to be threaded so I have screwed the brake in but it is upside down. I'm guessing that I should be able to move the nut from the other side to get it the right way around but it was stuck fast and I have rounded it out. Is there anything I can do or have I ruined the frame?

Nah....as long as the frame isn't split or anything nasty, you haven't ruined it. Post a couple of photos and we can advise if it's best to use a helicoil or set it up by more standard means. This will be quite fixable as long as you don't panic and do anything foolish while trying to fix it (at which point it could end up completely "fixed" lol).Zap some photos on from both the front and behind.

Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!Edit: 2015: darn near won the best South Island series (got second in age-group)..woo hoo Racy Theremery is back!!

Are you sure the brake bridge is threaded - I have had a lot more than 3 bikes and they have all worked the same way ! I have not had a C50 but my previous Colnagos were standard in this regard. Rather, is the bolt simply stuck in from the back side?

Can you remove the brake that you have threaded in, by unthreading it? I would do this, and then gently try to push out the bolt from the rear of the bike, having given it a generous spray of lube.

My first thoughts were that there was old bolt stuck in but I can't really tell. I contacted the seller of the frame and he reckons that:

'The nut isn't broken its intentionally fixed in the frame, the same with the later c40's you just screw the rear brake in and around and it will tighten in the perfect position'.

When I said that the brake screws in up side down he said:

'You can actually turn the bolt around inside, it's very tight but it does move'

The nut was definitely completely stuck before I rounded it, it wouldn't move either way.

No idea if he's making it up or not but not wanting to jump to any conclusions. I can screw the brake in and out no problem, if it wasn't the wrong way around I wouldn't mind. Couple of pics below but they don't show anything. I've only got an iphone, can't get anything better.

The bolt should not be "fixed" in the frame. I've had later C40's and C50's. They have always had the brake nut inserted from the rear and thread onto the brake post, as you said in your first post. Like someone else said, don't panic, you should be fine. Before you rounded the nut, did it spin at all, or did it round off before loosening? I believe it is stuck unless it has been altered in some way. Hopefully no one tried to epoxy it in there for some weird reason (bike people have been known to do weird things like that). You mentioned you used some penetrating oil... from which side? I would try this again, from the back side (closest to the down tube) and turn the frame so gravity will help with the fluid overnight. Then try that bolt you show in your photo again. Try wiggling it side to side to see if you can loosen it, even a bit, to satisfy yourself that it's not epoxied in there. If you have a powerful hair dryer (bike people have been known to do weird things to their hair), then maybe apply a bit of heat in the process. It should work loose. The pics are pretty good but I'm not there. If this fails I might take it to someone who you trust (and has some bike mech skills) so they can have a close up look at it in the flesh.

You may have even gotten it out by now, but you're doing the right thing. Finding out first if it's actually part of the frame or not. Good for you. It's not. So many people would just do some weird violent chant followed by a similar action (and it would probably work in this case), and then if they wrecked the frame then and only then would they search for answers to find out what they should have found out before they wrecked a perfectly good frame.

The guy you bought it from would seem a little suspect at this point as well for telling you what he told you. But maybe he legitimately deosn't know either. Good luck.

Find a steel M6 (?) nut and ditto matching washer. Screw it for a few cm onto the bolt you used before after you've lubed the threads of the bolt. Now screw the bolt onto the other side of the frame into the threading of the nut that's stuck in the frame for about at least 1/2 cm deep into that nut.Once you've done that find yourself a key that matches the nut you screwed on the bolt (should be a flat M6 if that's what the nut was) and start turning the nut clockwise so it approaches the frame.The washer serves as support area and will avoid scarring the frame. Keep tightening the nut whilst making sure the big bolt doesn't turn along as I assume it will screw right through the frame if you let it. As you continue to turn the nut against the washer the stuck nut will eventually be extracted out of the frame.

I'm assuming from what you wrote that you ruined the female hex part of the nut that's stuck and not the threading. If this doesn't work then the only thing left to do is to keep tapping the bolt with a rubber mallet from the brake side, it should become unstuck, eventually.

When the brake will be refitted make sure to use a nut that's long enough, preferably a steel or Ti one, not some cheap alloy thing. Put a couple of serrated washers over the brake's bolt, insert it into the hole, then fit the nut. By no means turn the brake to level it when the nut is tight already. Loosen the nut first, adjust and retighten the nut. No need to overtighten it either, that's how it gets pulled too far into the frame and gets stuck in the first place.

I was at my parents for Christmas so took it through for my dad to look at. In short it's still in there!

We thought the best idea was to try and get a bolt through from the inside and pull it out but are struggling to get past the hex bit where the allen key would go. We tried drilling through from the other side but the bolt is still too large a diameter to fit. I've left it with my dad and he is going to continue working on it but it looks as if I'm going to have to use a spacer so that the brake is the right way up when screwed in.